The 8 inch Howitzer was a leftover from the first world war. By 1939 only the Mark 8 was still in service. Several of them were left behind in France in 1940 so it was decided to replace it with the 7.2 inch. The carriage was to be used as it stood and the breech mechanism and any other useful bits incorporated into the new design. The gun was cannibalised out of service in 1941. Apart from some counter-bombardment work in France in 1940 and use as a training weapon, it played little part in the war. The 8 inch Howitzer was declared obsolete in July 1943.
Data
Weight of Gun & Breech Mechanism
7,560 lbs
Total Length
148.4 inches
Length of Bore
138.4 inches (17.3 calibres)
Rifling
48 grooves, uniform right hand 1/25
Breech Mechanism
Asbury interrupted screw, percussion fired
Elevation
0° to +45°
Traverse
4° right & left
Recoil System
Hydropneumatic variable, 24 to 52.5 inches
Weight in Action
20,048 lbs
Performance
Firing standard 200lb HE Shell
Muzzle velocity
1,500 feet per second
Maximum range
12,400 yards
Ammunition
Shell, HE Mark 15
Nose fuzed non-streamlined. Percussion Fuze No. 101E or 106E
The 12 inch Howitzer was first introduced in 1917. It was mostly an enlarged version of the 9.2 inch Mark 2 using a similar siege mounting. It was moved in six loads drawn by traction engines or Holt caterpillar tractors. It was no wonder the troops called it the “12 inch Road Hog”. It was provided with a power rammer which was probably the first ever used on a field equipment. Those guns still remaining in WW2 were deployed in 1940 in anti-invasion positions. In 1943 a “Siege Train” was proposed and an anti-concrete shell designed. The idea was dropped and the shells never produced. The 12 inch Howitzer was declared obsolete in March 1945.
Data
Weight of Gun & Breech Mechanism
20,440 lbs
Total Length
222.35 inches
Length of Bore
207.6 inches (17.3 calibres)
Rifling
60 grooves, uniform right hand 1/20
Breech Mechanism
Asbury interrupted screw, percussion fired
Elevation
+20° to +65° (loading angle +3½º hand, +19½º hydraulic)
Traverse
30° right & left
Recoil System
Hydropneumatic constant, 50 inches
Weight in Action
37½ tons plus 20 tons of earth in front box
Performance
Firing standard 750 lb HE Shell
Muzzle velocity
1,468 feet per second
Maximum range
14,350 yards
Ammunition
Shell, HE Mark 10
Nose fuzed, non-streamlined. Percussion Fuze No. 106 or No. 106E
Shell, Common Pointed Mark 1A
Non-streamlined, pointed with base Percussion Fuze No. 16. For hard targets
Shell, Concrete Piercing Mark 1
The requirement lapsed and it never entered production
Propelling Charge
2 distinct assemblies. Short Range Portion – charges 1 to 6. Long Range Portion – charges 7 to 11.
In September 1934 a pilot model for a new 25 pdr Gun was ordered. To keep down costs it was decided to produce an auto-frettaged loose barrel that could be inserted into the jacket of the existing 18 pdr. This would then be fitted to the 18 pdr Mark 4P or Mark 5P carriage. This became known as the 25 pdr Gun Mark 1 (18/25 pdr). At the same time development continued on a complete 25 pdr gun and carriage hoping funds would become available later.
Official approval for the 18 pdr conversion was given on 26th August 1936 as the Ordnance QF 3.45 inch Mark 1. In February 1938 this was changed to Ordnance QF 25 pdr Mark 1. However it was mostly known by the name ’18/25 pdr’ as this was the more accurate description. Over 1,000 of the 25 pdr Gun Mark 1 (18/25 pdr) were produced.
’18/25 pdr’ on Mark 5P Carriage
Data
Weight of gun & breech mechanism
991 lbs
Total length
96.725 inches
Length of Bore
92.365 inches
Rifling
Polygroove, plain section
Firing mechanism
Percussion
Performance
Muzzle velocity
1486 feet per second
Maximum range
11,500 yards
Ammunition
As for the 25 pdr Mark 2 except Supercharge could not be fired
The 18 pdr Gun was introduced in 1904. More than 10,000 were made of the original model. Work began in 1916 on an improved design but it wasn’t until 1918 that it went into production as the Mark 4 Gun on Mark 3 Carriage. This was a big improvement with a box trail and Asbury breech mechanism. It became the standard field gun in the post-war years. It was improved still further in later years with a split trail carriage and pneumatic tyres. By the end of its life there had been five Marks of Gun and five Marks of Carriage with many sub-Marks in each.
When the 25 pdr Mark 1 was introduced, a number of 18 pdrs were coverted by simply changing the barrel. As the 25 pdr took some time to come to full production, the 18 pdr stayed in service for most of WW2. Eventually, the Mark 4 was made obsolete in August 1940 as the last one was converted to 25 pdr. The rest remained in use until 1944 having been used for training and then anti-invasion defences in 1940-41. They were also used in the Middle and Far East.
Gun
Mark 1
Original pattern. Wire-wound, screw breech, 1904
Mark 1*
Mk 1 repaired by insertion of new ‘A’ Tube and wire. Gun assembled by hydraulic pressure
Mark 2
Gun assembled by hydraulic pressure instead of heating/shrinking 1906
Mark 2*
Mk 2 converted for AA mounting in 1915. Converted back in 1920
Mark 3
Development model not adopted 1917
Mark 4
New design, Asbury breech mechanism 1918
Mark 4A
Mk 4 repaired by replacement of ‘A’ Tube & wire by auto-frettaged loose liner 1935
Mark 4B
As Mk 4A but new manufacture 1935
Mark 5
As Mk 4 but differences to suit Birch Gun mounting 1926
Carriage
Mark 1
Original, pole trail, hydro-spring recoil, elevation 16º 1904
Mark 1*
Mk 1 modified to hydropneumatic recoil system 1916
Mark 1R
Mk 1 with solid rubber tyres
Mark 1*R
Mk 1* with solid rubber tyres
Mark 1**
Mk 1 * with lengthened cradle
Mark 1C
Mk 1 with extended cradle
Mark 1D
Mk 1 with Mk 2 Carriage cradle
18 pdr Mark 2PA
Mark 2
Similar to Mk 1 but hydropneumatic recoil system & longer cradle
Mark 2*
Mk 1* but with Mk 2 Carriage cradle
Mark 2PA
‘Martin Parry’ conversion, pneumatic tyres on steel disc wheels
The Morris Commercial C9B 40mm Bofors SP was developed as a private venture by Morris Commercial. The chassis was a lengthened version of their C8 Field Gun Tractor and was fitted with a platform at the rear for the gun and an open cab with seating for a driver and three detachment members. The cab had no roof, doors or windscreen to allow the gun all round traverse. The steering wheel column was hinged to allow the wheel to be folded down out of the line of fire. A canvas cover was provided for bad weather which covered the cab allowing the men’s heads to protrude. There were scissors jacks fitted front and rear with one each side on folding outriggers. The gun was fitted on the Mounting Mark 5.
The C9B 40mm Bofors SP began development in 1941 and was in service from 1943. It was originally conceived as mobile protection for convoys and columns. It served in all theatres of operation.
The 18 inch Railway Howitzer was suggested in 1917 as a partner to the 14 inch Railway Gun using the same carriage. There were no existing guns of that calibre, so a new gun was designed. It was to have the same profile and size of the 14 inch Gun so that it could fit the 14 inch’s carriage without modification. Despite the difference in size, this was possible because the stresses on a howitzer barrel were much less than on a gun and therefoe allowed the barrel walls to be thinner. The design was finished in 1918 and two barrels were made. They were not completed in time for the war and so were mounted, proofed and then put in store.
In 1926 the 14 inch was made obsolete and scrapped but the carriages were retained. One of the 18 inch barrels was mounted on HMG Boche-Buster and taken to Salisbury Plain. During the inter-war years the gun was fired twice. In 1940 it was sent to Dover to become part of the invasion defences at Bekesbourne on the Dover/Canterbury line. Being a howitzer it barely had the range to cover the beaches of the Kent coast. It was never fired in anger and doubtful if it fired much in training either. In 1943 it was back on Salisbury Plain firing trials of a new anti-concrete shell. This is probably the last time it ever fired.
Late in 1943 it joined the 13.5 inch guns in a Super Heavy Railway Regiment. The idea of using the regiment in the invasion was soon dropped and the regiment disbanded. The 18 inch Railway Howitzer was declared obsolete in April 1947 and later scrapped.
Data
Weight of gun & breech mechanism
191,968 lbs (85 tons)
Total length
648.4 inches
Length of Bore
624.6 inches (35 calibres)
Rifling
72 grooves, uniform Right Hand 1/20
Breech mechanism
Interrupted screw, continuous motion, electric & percussion fired
Elevation
0º to +40º
Traverse
2º right & left
Recoil system
Hydropneumatic, constant 34 inches
Weight in action
560,935 lbs (250 tons)
Performance
Firing standard 2,500 lb HE Shell
Muzzle velocity
1,880 feet per second
Maximum range
22,300 yards
Ammunition
Separate loading, bag charge
Shell, HE Mark 2D
Streamlined, nose fuzed shell weighing 2,500 lbs. Fitted with Percussion Fuze no 231
Shell, CP, BC, S/L Mark 1D
Common Pointed shell with Ballistic Cap & Streamlined base. Fitted with Base Percussion Fuze No 270
Shell Anti-Concrete S/L Mark 1D
Approved 1944, an advanced design. Concave head under a ballistic cap. Fitted with Base Percussion Fuze No 270
Propelling charge
7 charge options in 2 portions, long & short range. Charge 1 Short range + increments 2, 3 & 4 total weight 182 lbs of Cordite. Charge 5 Long range + increments 6 & 7 total weight 282 lbs of Cordite
The 13.5 inch Gun was a combination of an obsolete mounting with an obsolescent gun as an emergency measure in 1940, when there was no long range heavy artillery available. The War Office appointed Lt Col Cleeve RA, one of the few remaining railgun experts to search for anything suitable that might be available. He knew there were some 14 inch railway mountings still available and he found some 13.5 inch guns in an Ordnance Depot near Nottingham. They had come from the Iron Duke class battleships and were close enough to the obsolete 14 inch guns to be fitted in the 14 inch mountings. It was decided to fit out three guns.
The first gun was delivered on the 20th September 1940 with the other two being completed by May 1941. The next problem was finding men to operate them. The army was unable to provide men but the Royal Marines, already operating two 14 inch guns near Dover, had men to spare so took over the three guns. The guns were all named using the same names they had in France in 1917-18. They were all sited in the area of Dover as follows: HMG Scene Shifter at Lydden on the Dover/Canterbury line. HMG Gladiator at Martin Mill on the Dover/Deal line. HMG Piecemaker at Guston Tunnel on the Dover/Deal line.
The guns had two roles. Covering possible landing beaches in Kent and firing on the enemy positions in the area of Calais. This they could just reach firing Supercharge. The guns were not used very often as aiming required the gun to be pushed along a convenient curve in the track. Nor were they immune from attack theirselves. On the 10th December 1940 a 28 cm shell fell within feet of ‘Piecemaker’ damaging a bogie and killing a Marine. In November 1943 the guns were handed back to the army and withdrawn from the Dover area. They were formed into a Super Heavy Regiment RA and began training for the forthcoming invasion of Europe. In the event they were not required and the guns were declared obsolete in 1945.
The 13.5 inch Mark 5 Gun had entered service in 1912. It was a wire wound gun mounted on a simple box. The mounting was carried on two 4 axle bogies at the front and one 4 axle and one 3 axle bogies at the rear. A limited amount of traverse was provided by hauling the front end of the mounting across the bogie bolster. This was achieved by the use of warping winches at the trackside which were connected by cables to the mounting. The mounting did not move on firing.
Data
Gun Mark 5 on Railway Mounting 14 inch Mark 1
Weight of gun & breech mechanism
170,520 lbs
Total Length
625.90 inches
Length of Bore
607.50 inches (45 calibres)
Rifling
68 grooves, uniform Right Hand 1/30
Breech mechanism
Interrupted screw, electric or percussion fired
Elevation
0º to +40º
Traverse
2º right & left
Recoil system
Hydropneumatic, constant 34 inches
Weight in action
539,224 lbs (240 tons)
Performance
Firing standard 1,250 lb Shell
Muzzle Velocity
2,550 feet per second
Maximum Range
40,000 yards
Ammunition
Separate loading, bag charge
Shell, HE, Mark 0
Base fuzed Armour Piercing shell. Standard Naval pattern
Propelling Charge
Bagged 293 lbs of Cordite in 6 sections for ease of handling
The 7.2 inch Howitzer was developed from the 8 inch Howitzer. In July 1940 there was a severe shortage of heavy artillery and a demand was raised for a new gun of about 8 inch calibre with greater range than the existing 8 inch Howitzer. It also needed to be on the same sort of carriage as the 8 inch Howitzer. In August 1940, trials were carried out to determine how much stress the carriage and recoil system of the 8 inch could stand. As a result, development was started on a 7.2 inch Howitzer firing a 200 lb shell with a maximum muzzle velocity of 1,700 feet per second.
Existing 8 inch Howitzers were taken to workshops where the barrel liner was removed and replaced with a 7.2 inch liner. Alterations were made to the breech mechanisms to suit the new calibre. This new weapon was then introduced as the 7.2 inch Howitzer Mark 1. It was officially approved on the 7th April 1941. A little later, American 8 inch Howitzers were bought and converted to 7.2 inch in the same way.
There was a problem with the recoil as the force was more than the recoil system could absorb fully. As a result the carriage moved backwards on firing and on wet ground this movement could be unpredictable and dangerous with the crew having to stand well clear of the gun before firing. To try and control this movement, large wedges were placed behind the wheels so that on recoiling the gun ran up the slope of the wedge and back down again. Even with these wedges, firing was still daunting for the crew. Early in 1943 it was decided that with Charge 4 the gun was not fully under control and so a search began for a new carriage.
The American 155 mm Gun M1 started to arrive in the UK. Its carriage could be adjusted to take the US 8 inch Howitzer so in April 1943 a trial fitting was made of the 7.2 inch. It was successful and the combination was approved in November 1943 as the 7.2 inch Howitzer Mark 5. At the same time a new, more powerful howitzer was being prepared. A completely new design, 33 calibres long, it was approved and adopted on the 21st December 1943 as the Mark 6 Howitzer. As a result the Mark 5 was never issued for service.
7.2 inch Howitzer Mark 6
The Mark 6 increased the maximum range by about two miles and became the standard equipment of Heavy Regiments. It remained in service into the 1960’s.
Gun
Mark 1
Converted from 8 inch Howitzer Mk 8
Mark 1*
Mk1 repaired by insertion of inner ‘A’ tube into worn barrels
Mark 2
Conversion of ex-US 8 inch Mk 6
Mark 3
Conversion of ex-US 8 inch Mks 7, 7* &7**
Mark 4
Conversion of ex-US 8 inch Mk 8 or 8½
Mark 5
Conversion of Mk 1 to suit US 155 mm mounting
Mark 5*
Conversion of Mk 1* to suit US 155 mm mounting
Mark 6
New construction, 33 calibres long to suit US 155 mm mounting
Mark 6/1
Mk 6 repaired, body prepared for shrunk in ‘A’ tube
The 4.5 inch Anti-Aircraft Gun was a Naval gun, adopted for the army in place of a 4.7 inch gun that was being developed in the 1920’3 and early 30’s. Because, in 1937, priority was given to the 3.7 inch gun there was little chance of getting the 4.7 inch into production. The 4.5 inch on the other hand was already in production, the ballistics were close to the projected 4.7 inch and as most of the places the army intended deploying the guns were near Naval installations, ammunition supply through the Navy was assured. The gun was therefore approved for land service in 1938 as the 4.5 inch gun Mark 2.
The gun had a loose liner and short jacket with a horizontal, sliding breech block. the mounting was static although it could be moved on a special Transporting Limber. The rear trunnioned gun was balanced by a heavy counterbalance on a cantilever arm at the rear. An electric rammer was fitted in 1940 giving a rate of fire of 8 rounds per minute. The mounting was fitted with an open back, mild steel shield.
In 1940-41 some guns were used in a dual Anti-Aircraft/Coast Defence role sited near the coast. They were supplied with a semi-armour piercing shell for usr against targets at sea. Other than those guns, ground targets were only ever to be engaged in a dire emergency.
The 4.5 inch Anti-Aircraft Gun was mostly superseded by the 5.25 inch gun in 1944-45. It was only declared obsolete in 1951. There was no variant models of the gun, all other variants being Naval guns. There were two variants of the mounting, the second being the Mark 1A allowing more depression for coastal mounted guns.
The 17 pdr Gun SP M10 was essentially the 3 inch Gun Motor Carriage M10 with the gun changed for the more powerful 17 pdr. Conversion began in April 1944 but by the 6th June (D Day) only 124 had been converted. Production was increased and by the end of the year 816 had been completed. By the end of the war about 1,100 had been converted.
There is still some uncertainty as to where and when the name Achilles was applied to the vehicle but in service they were generally referred to by their crews as the M10 17 pdr. Depending on which version of the M10 the conversion was based on the designation IC or IIC was added i.e. 17 pdr Gun SP M10 IIC.
Gun
Mark 6
Mk 1 with altered breech ring to suit M10 mounting
